1. Field of the Invention
The invention relates to a liquid-crystal mixture with an anthraquinone derivative and relates further to a method for synthesizing the anthraquinone derivative. A liquid-crystal solution of this kind is described in German Patent Application P 30 07 198.8.
2. Description of the Prior Art
The known dyes which are suitable for liquid-crystal displays absorb only in a relatively limited range of the visible frequency spectrum. They must therefore be mixed together if a black picture or a black background or as large a bright-dark contrast as possible is desired. In practice, the preparation of such mixtures presents considerable difficulties. Again and again it was found that a mixture that has a reasonably acceptable absorption spectrum, is not soluble enough and/or is not stable enough with all its components. These problems are related to the fact that the mixtures examined so far do not have the suitable components.